viernes, 18 de mayo de 2012

Particularly Dangerous Salmonella Discovered

The new Salmonella strain is up to 100 times more capable of causing disease.
Salmonella enterica is a significant food-borne pathogen of humans causing up to an estimated 1.3 billion cases of disease worldwide, annually. The diversity of salmonellae present on farms and feedlots, and the potential for different serovars to possess an array of virulence attributes, necessitates the use of broad prophylactic strategies that are efficacious for many serovars simultaneously.
Hyper-infectious Salmonella are among the most virulent of this species; restricted to certain serotypes; and more capable of killing vaccinated animals. Such strains exhibited rapid (and rapidly reversible) switching to a less-virulent state accompanied by more competitive growth ex vivo that may contribute to maintenance in nature. The hypervirulent phenotype was associated with increased microbial pathogenicity (colonization; cytotoxin production; cytocidal activity), coupled with an altered innate immune cytokine response within infected cells.
Gene expression analysis revealed that hyper-infectious strains display altered transcription of genes, conferring changes in the expression of classical Salmonella virulence determinants (e.g., SPI-1; SPI-2 effectors) and those involved in cellular physiology/metabolism (nutrient/acid stress).

These "hyper-virulent"Salmonella can override vaccines and pose a risk to food safety. Previous strategies to find the more dangerous bugs were unsuccessful since they behave like a "Trojan Horse" -- exposing their weapons only when causing disease -- but looking much like their less-virulent cousins in the environment.
Now that scientists know what to look for, they are developing methods to discriminate them from their less-virulent cousins. The researchers have been successful in forcing Salmonella to reveal their weapons in the laboratory -- the first step in combating them.
From a farm management perspective, careful consideration must be given to risk-management strategies that reduce emergence/persistence of these hyper-virulent potential food-borne contaminants to safeguard public health and reduce industry-associated losses.

Aporte: Sebastián Pizarro

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